The oxidizing action of ozone and the antimicrobial action of ultraviolet radiation are well known, with both agents enjoying widespread use for decontaminating household water supplies. It is known to provide a decontamination apparatus that employs both agents to purify water within an integrated or dual mode system. Such systems are disclosed in, among other references, U.S. Pat. Nos. 4,141,830 (Last); 4,179,616 (Coviello et al.); 4,230,571 (Dadd); 4,189,363 (Bietzel) and 4,273,660 (Bietzel). A typical dual mode system includes an ozone generator, such as a UV lamp, and a reaction chamber, or "contactor", to expose the contaminated water to the ozone. The UV lamp also exposes a second chamber, wherein the water is irradiated. Typically, the first and second chambers comprise coaxial jackets surrounding the UV lamp, with the inner jacket being the air exposure chamber and having a housing made of a material that allows germicidal radiation to pass through to the outer, second jacket. Typically, there are also provided gas and fluid conduits and valves, as well as pumps and various means to combine the ozonated gas with the fluid. There may also be provided water filters at various positions in the device, as well as pressure regulators, valves and other components necessary for the smooth and regulated flow of water and gas through the system. A control unit may be provided to control the operation of the system, with means to control the flow rate of gas and water, and a timer to preset the operation of the device.
A drawback of existing systems resides in the power consumption and limited lifespan of UV lamps. In order to address this, it is desirable to provide a means to control the intensity of the UV lamp, in order that the lamp intensity may be attenuated when the system is not in active use. Preferably, the control should operate automatically, such that flow of water through the device automatically triggers an increased lamp intensity, and vice-versa. As well, the lamp output may be attenuated when the lamp temperature exceeds a predetermined amount; in this case, an automatic control should be provided that shuts off the flow of water through the system. In order to achieve optimal operation of the device, the rate of flow should be controlled in order that an optimal flow rate is achieved while the system is in active use.
A further advantage in such a system may be achieved by maintaining a relatively high pressure within the fluid stream. Typically, a system for the supply of potable water is linked to an incoming household water main, and is required to discharge water under pressure. Accordingly, it is desirable for the whole system to operate at the household water pressure. Efficient operation of the system may be achieved by providing treatment of water in batches, rather than strictly on a demand basis. Previous such devices, for example, U.S. Pat. No. 5,213,773 (Burris) have relied on an unpressurized (or lightly pressurized) tank for the storage of treated water, with the system being actuated to process a batch when a float switch indicates a drop in fluid level within the tank. This type of system is not well adapted to supply treated water under pressure.
In a system operating at household pressure, it is desirable to provide a means to maintain a pressurized holding tank, in order that the treated water may be discharged under pressure. Upon discharge of a sufficient quantity of treated water from the tank, with a consequent pressure drop within the tank, a control system may be provided to actuate the system to recharge the tank.
Since decontamination systems are often employed for home use, it is desirable to provide a relatively compact unit. This requirement poses a particular difficulty in the case of dual mode systems, with their relatively large number of components. This requirement may be addressed, in a dual mode system, by providing a contactor that comprises a helical coil, as described in applicant's co-pending application Ser. No. 08/189,645, that coils around one of the water filters.
The present invention has as its object the provision of a UV-based fluid decontamination system that delivers treated water under pressure, while minimizing energy consumption and maximizing bulb life. It is a further object to provide a dual mode system that is relatively compact, provides a high degree of purification to the contaminated water, and employs a high degree of automation in its operation. A further object is to provide a system that automatically provides a batch treatment of contaminated water, with the system switching automatically between standby and active modes in response to water demand and in response to bulb overheating.